1. Field of the Invention
The present invention relates to a slider on which a transducer for a disk apparatus, etc. is mounted and which moves relatively above a recording surface, and more particularly, to a slider on which piezo-electric elements are disposed and a disk storage apparatus having the slider.
2. Description of the Prior Art
In a magnetic disk apparatus, a slider with a mounted transducer is raised by a high-speed air flow caused by a disk that rotates at a high speed and data is written or read to or from the recording surface of the disk during relative motion of the transducer and the disk. Such a slider is fixed to a suspension. In order to keep the slider flying at a predetermined height (sub micron) above the recording surface, resilient force urging the slider toward the recording surface against the buoyancy of the high-speed air flow is always applied to the slider by the suspension.
Therefore, if the speed of rotation of the disk decreases and the buoyancy of the high speed air flow becomes no longer enough to support the slider, the slider will run into the recording surface and recorded data will be destroyed. To avoid this, when the disk is at rest or its rotation is not enough for the buoyancy, conventionally, a mechanism for raising and supporting the slider above the recording surface is provided, or the slider is moved into an area (landing zone) not used for recording data on the disk but used for landing or sliding.
The latter method in which the slider retreats to the landing zone at the rest time of the disk and slides on the landing zone when the buoyancy is not enough, is called contact start and stop method (CSS). This method is widely used because it has the advantages of greater simplicity in construction and reduced cost in comparison with the former method in which the slider is raised and supported by a mechanism.
However, in the contact start and stop method, at the time when the disk starts to rotate from its rest state torque requirement, that is, power requirement increases due to friction between the disk and the slider, or if the slider is stuck into lubricant film applied on the landing zone when it is at rest, this phenomenon is called stiction, the slider and the lubricant film may be damaged if the slider is forced to break away the lubricant film. Further, it would be a problem that rubbing of the slider which slides on the landing zone causes dust to be blown up and results in contamination. Still further, when the slider slides on the landing zone, smooth sliding is not actually done so that the slider will collide repeatedly with the surface of the disk many times and the disk and the slider will receive a shock. Therefore, both of them are required to have mechanical strength to some extent.
To solve such problems, prior art makes the air bearing surface (ABS) of the slider contacting the recording surface convex or to fabricate the landing zone rough, that is, fine convexities and recessions are provided on the surface, in order to decrease the area of contact between the slider and the recording surface so far as the extent allows and to reduce friction or stiction. However, the above method leaves room for discussion in terms of the accuracy of works.
Further, conventionally, it is proposed that piezo-electric elements are mounted on the slider. The piezo-electric elements are used for arbitrarily changing the degree of the evenness of the air bearing surface (ABS) (Japanese Published Unexamined Patent Applications (PUPAs) No. 1-166382 and No. 3-144979) or for making a transducer element projected form the ABS while the slider is flying and making it retreated at the time of slider's landing (Japanese PUPA No. 61-194684).
In which case of Japanese PUPAs No. 1-166382, No 3.-144979, and No. 61-194684, piezo-electric elements are disposed on a slider of contact start and stop type and stiction to a landing zone can be weakened and the floating height can be adjusted by changing the shape of the ABS, but if a disk rotates at less than the rotational velocity enough to support the slider, it would be a problem that sliding occurs between the slider and the disk and results in the increase of torque due to friction and occurrence of contaminating particles due to rubbing.
Further, it is conventionally known that a film of compressed air is formed by vibrating piezo-electric elements at a high frequency, and thereby an object is supported (Refer to Pages 172 to 216 of TRIBOLOGY Friction, Lubrication, and Wear Edited by A.Z.Szeri, Copyright 1980 Hemisphere Publishing Corporation).
Still further, an attempt to dispose one piezo-electric element on the slider of a disk storage apparatus to raise the slider by applying AC voltage to the piezo-electric element was made by W.D.Koperski and G.A.Domoto at Columbia University in New York in 1981.
Construction attempted by Koperski et al is such that high-frequency vibration caused by the piezo-electric element vertically raises and lowers the slider and has the possibility of solving, by one effort, the above problem on sliding between the disk and the slider at the time when the disk rotates at less than the rotational velocity to support the slider.
However, in the construction attempted by Koperski et al, only one piezo-electric element is disposed on the slider, and therefore the number of modes, in which the slider is vibrated by the piezo-electric element, is very restricted and it is scarcely possible to change the vibration mode of the slider according to situation.
For example, when stiction occurs between a slider and a disk, rolling (oscillation around the longitudinal axis of the slider) or pitching (oscillation around the transversal axis of the slider) motion for removing the slider from the disk shows a more effect than even up-and-down motion. In the construction attempted by Koperski et al, however, it is difficult to generate vibration of such various modes in the slider.
Besides, if the slider floats through the high-speed air flow while the disk rotates at an operational velocity, it is difficult for the construction attempted by Koperski et al to apply a controlled AC voltage (for example, of the same or reverse phase, etc.) to each of piezo-electric elements disposed at a plurality of positions of the slider in order to change the floating height and posture of the slider.